Time of Flight

It is the total amount of time the projectile remains in the air.

In Y direction total displacement (S_y) = 0.

Taking motion in Y direction, S_y = u_yt – 1/2(gt²)   

(Here, u_y = u sinθ and S_y = 0)

i.e.      0 = usinθ – 1/2(gt²)

t = 2usinθ/g

Time of Flight(t) = 2usinθ/g